using System;

​

public class Person

{

    public int id{get;set;}

    public string ten{get;set;}

    public int namsinh{get;set;}

}

public class Studen:Person

{

    public double demob1{get;set;}

    public double demobo2{get;set;}

    public double demobo3{get;set;}

}

public class Program

{

    public static void Main()

    {

    }

}